Method of sulfurizing terpene hydrocarbons



Patentecl June 23, 1953 METHOD OF SULFURIZING TERPENE HYDROCARBONS ElmerW. Brennan, Chicago, Ill., assignor to The Pure Oil Company, Chicago,111., a corporation of Ohio No Drawing. Application May 2, 1950,

Serial No. 159,660 7 1'? Claims. (Cl. 260-139) This invention relates tothe sulfurization of isoprenoid compounds having an alicyolic structure,as for example, the various terpenic hydrocarbons including both themonoand dicyclic terpenes. More particularly, this invention relates toa method of preparing sulfurized terpene hydrocarbon products by thereaction of terpenes with sulfurizing agents and promoting the reactionby the presence of lead oxides.

In a related application entitled Method of Sulfurizing TerpeneHydrocarbons, Serial No. 136,157, filed December 30, 1949, it wasdisclosed that the sulfurization and phosphorization of terpenichydrocarbons, to form lubricating and cutting oil additives, could bepromoted by conducting the reaction in the presence of varioussulfurization promoters, such as phosphorus sulfides, phosphoruschlorides, and sulfur chlorides. It has been discovered that anotherclass of compounds, namely, lead oxides and their corresponding plumbicand plumbous salts, also serve to promote the sulfurization reaction toyield a product having a preponderance of desirable qualities as anadditive and, at the same time, the reaction is free from excessivesludging and polymer formation. The product is found to be morecompatible with mineral oil when made in accordance with thisinvention.v

The reaction of isoprenoid compounds with sulfurizing agents, and inparticular, free sulfur, has long been practiced to yield a productwhich, when compounded with lubricating oils, imparts desirableproperties to the composition, such as, oxidation stability andnon-corrosiveness to alloy bearings. isoprenoid compounds is generallyrecognized to be one of the addition of the sulfur to the double bondspresent in the molecule and a splitting off of water with thoseisoprenoids containing oxygenated groups. The products resulting fromthe reaction are complex and have been identified only partially asmono-, di-, and tetra-sulfides of the terpenic molecule. Thesulfurization art has long recognized the importance of placing sulfurin the organic molecule in a form which is non-corrosive and yet activefor the purposes desired. Ordinary sulfurization methods do not in allinstances accomplish this result since uncombined sulfur is oftenpresent in the product,

which crystallizes out when the reaction mass 7 is cooled or the productmay lose its free sulfur after it has been compounded with a lubricatingoil. With certain starting materials, like the terpenes, the reactionmay produce a product containing corrosive sulfur in the form of hy- Thedirect addition of sulfur to r drogen sulfide incorporated in thereaction mass or a portion of the terepene may react to producemonosulfides and mercaptans which are also corrosive. If water is formedduring the reaction there results the formation of sulfurous acids inthe presence of sulfur in this corrosive state and the undesirability ofthe product is increased. In addition, the presence of water in theproduct tends to produce a cloudy appearance in the final compositionwith the lubricating oil with the result that it is unmarketable or maybecome so on standing or storage. Often when the sulfurization reactionis conducted at too high a temperature the terpene molecules arepartially cracked and these cracked products tend to reduce the flashpoint of the final product.

' Many attempts of greater or lesser success have been made to improvethe product of the sulfurization of terpenic hydrocarbons. If steamdistilled pine oil, a typical terpene obtained from the distillation ofcrude turpentine, and having as its main constituent alphaterpineol, B.P. 217 to 218 0., being an alcohol of the cyclohexane series oftendesignated as a monocyclic terpene, is heated with elementary sulfur, asthe temperature rises the sulfur melts and begins to dissolve in thepine oil. At about 350 F. ebullition takes place and an exothermicreaction sets in with consequent rise in temperature to about 375 F., atwhich point sulfur is dissolved and complete homogeneity is reached. Ifthis mass is cooled the sulfur tends to crystallize out and the productwill have a low sulfur content and a high polymer content, in additionto exhibiting most of the other undesirable characteristicsaforementioned. By prolonged heating of the sulfur and pine oil afterhomegeneity, some of these difficulties can be eliminated. What has beensaid of pineroil is generally true of the other members of the class ofisoprenoid compounds. Although numerous methods have been found toeliminate most of the difficulties enumerated, the means employed areoften tedious, time-consuming and expensive.

It has been discovered that the sulfurization of terpene hydrocarbons,at a temperature of at least about the melting point of sulfur and notbelow the temperature at which free sulfur precipitates, can bematerially accelerated and promoted by conducting the reaction in thepresence of lead oxides, including lead tetraoxide, Pb304, leadsesquioxide, Pb203, lead peroxide, PbOz, lead monoxide, PbO, leadsuboxide, PbzO. Instead of the lead oxides, the-metal salts of plumbic,metaplumbic, orthoplumbic and plum- 6 bous acids may be used. Examplesof these salts are calcium orthoplumbate, potassium metaplumbate, andsodium plumbite.

Accordingly, it is the main object of this invention to provide a methodof promoting sulfurization of terpene hydrocarbons and particularly,monoand dicyclic terpenes.

It is a second object of this invention to provide lead oxide promotersfor the sulfurization of terpenes and a method for conducting thepromoted reaction.

It is a third object of this invention to provide as sulfurizationpromoters various lead oxides and salts such as: lead tetraoxide, leadsesquioxide, lead peroxide, lead monoxide, lead suboxide, calciumorthoplumbate and potassium metaplumbate.

It is a fourth object of this invention to provide a method for thesulfurization of terpene hydrocarbons wherein the chemical combinationof the sulfurizing agent and the terpene is materially aided, therebyyielding a final product having an increased sulfur content and areduced polymer or side reaction product content.

Other objects will become apparent from the following description of theinvention.

In conducting the sulfurization of vterpenic hydrocarbons, in accordancewith this invention, the terpenes and sulfurizing agent, such aselemental sulfur, and lead oxide promoter, are mixed thoroughly and themixture heated under reflux at atmospheric pressure, to a temperature ofabout 248 to 435 F. This temperature range has for its lower limit themelting point of sulfur and as its upper limit the end boiling point ofpine oil and represents the broad temperature limits in which thereaction may be conducted. Temperatures of about 240 to 248 F. aresufficient to create a homogeneous mass but the rate of reaction of thesulfur with the terpene is slow. If a closed system is used for thereaction and pressure is allowed to build up, due to any vaporization ofreactants, then temperature adjustments, by control of rate of heatingand amount of pressure, between 248 to 435 F. or beyond, are possible.The preferred temperature of initial heating is between about 300 to360F. at which temperature the sulfur within the homogeneous mass begins toreact at an appreciable rate with the terpene. action takes place and nofurther heating is necessary for a period of about 30 to 60 minutes,depending on the mass of reactants and the rate of heat dissipation.

As soon as the exothermic reaction begins to subside, that is, at leastbefore the mass has cooled to the point wherein sulfur begins toprecipitate, about 200 F., heat is again applied and the reactiontemperature maintained at about 300 to 400 F., preferably at about 310to 350 F., for a period sufficient to complete the reaction of reactablesulfur with the terpene. When the reaction mass is under reflux,sufiicient heat may be applied to keep the mass at its boilingtemperature. This temperature will. vary with the type of terpene used.This last heating period is variable between about 4 .to 16 hours,depending on the nature of the terpene being treated and the averagereaction temperature maintained.

The end point of the reaction is determined by withdrawing a portion ofthe mass, cooling to room temperature, and allowing it to stand. Theprecipitation of any unreacted sulfur is an indication that the reactionis incomplete. If too large an amount of sulfur, over the stoichiometricex- At this point, an exothermic rea cess, is employed, no amount ofheating will prevent sulfur precipitation on cooling. Proportions ofsulfurizing agent and terpene are adjusted to maintain approximatelyenough sulfur present to yield a product containing from about 20% tothe amount which it is possible to stoichiometrically react with theterpene. The promoter may be incorporated at the beginning of thereaction or added in increments during the reaction, to allow thoroughdispersion of promoter in the sulfur-terpene mass.

The final product, resulting from this reaction, may be used as acutting oil additive or a lubrieating oil additive. Whether or not theend product is purified will depend on the use that is to be made of it.Cutting oil additives do not require strict purification, whereuponlubricating oil additives will require some purification and removal ofunreacted low boiling constituents therefrom.

The total amount of sulfur used should, of course, be at least equal tothe amount stoichiometrically necessary for combining with allof theterpene present. However, good practice dictates that an excess of from5% to 10% is preferable, although the use of larger than 10% excess issometimes expedient. Although sulfur is the preferred sulfurizing agent,the process may be carried out using other sulfurizing agents ashydrogen sulfide and the sulfur halides. The choice of the particularsulfurizing agent, or mixture thereof, will depend on the type .ofproduct desired.

The advantages of the present invention are more fully pointed out bycomparison of the following examples:

Erample 1.-% by weight Dipentene 122 and 15% by weight sulfur were mixedand heated to 330 F. at atmospheric pressure under reflux for 30 hours.During the reaction and at the completion of the experiment the reactionproduct contained a large quantity of free sulfur and unreacteddipentene. The product was not compatible with mineral oil and exhibiteda precipitation in the form of polymer insolubles when added thereto.The same result was obtained when using 70% by weight of Dipentene 122and 30% by weight of sulfur for the reaction. The product displayed avery loose black scale on subjection to the copper strip test.

Example 2.58% by weight of dipentene and 42% by weight of sulfur wereheated together at atmospheric pressure under reflux. After 30 hours ofheat at 335 to 348 F., the product contained a large amount of freesulfur and unreacted dipentene. In addition the product was unfit foruse with a mineral oil due to its polymer content, color and loose blackscale on copper strip test.

Example 3.-60% by weight of Dipentene 122, and 42% by weight of sulfur,with 1% of red lead, Pb304, based on the weight of Dipentene 122 used,were heated together under reflux at atmospheric pressure to atemperature of 330 F. When the temperature reached about 330 F., anexothermic reaction occurred which maintanied the reaction temperatureat about 330 F. for about 40 minutes. During this period, it wasunnecessary to add heat. When the exothermic reaction had subsided, heatwas again applied and the temperature maintained at about 330 F. forabout 5 hours. A sample .of the reaction mass, at this point, when heldat room temperature for about 15 hours, gave no signs of theprecipitation of free sulfur. The main reaction mass was heated for aperiod of about 1'7 hours and filtered. The final sulfur content was23.9%. There existed a residue from the filtration, having theappearance and characteristics of a material not unlike leadmonosulfide, PbS. The product gave a copper strip test which wasiridescent, was completely compatible with mineral oil and imparted noundesirable color characteristics thereto.

The foregoing examples illustrate the improvement attainable whenthesulfurization reaction is promoted using lead oxides. The copperstrip test mentioned is conducted for the purpose of indicating theactivity of any sulfur that may be present. The test serves as a guideto the chemical characteristics and possible uses or applications of theproduct. The copper strip test is conducted by immersing a polishedcopper strip in the reaction mixture, or in a sample of the finishedproduct, maintained at a temperature Of at least about 300 to 330 F. forone to three minutes. The test results are ascertained by observance ofthe color of the copper strip. The color observed will vary from apeacock color to a black discoloration. Intermediate between theseextremes is an iridescent to grey or dark grey coloration, the latterindicating a borderline product as far as use thereof for lube oiladditive purposes is concerned, and the former indicating a passableproduct for the same purpose. The grey or black strips may or may not beaccompanied with a loosely bound sulfide scale.

The lead oxides and plumbate or plumbic salts, used in accordance withthis invention, may be of the ordinary commercial variety. For example,red lead, having a molecular weight of 685.83, and containing 0.01% acidinsoluble matter, 0.000% chlorine, 0.005% nitrate, 0.005% copper, 0.002%iron, and 0.0001% manganese, is operable for use as a promoter herein.

Thus, it is apparent that by conducting the sulfurization of terpenes inthe presence of lead oxides, an improved product can be obtained in ashorter time, with the use of less heat, and the sulfur content of theproduct is more tightly bound in the terpene molecule. The sulfurizedproduct is more compatible wtih mineral oils and imparts an increasedoxidation resistance thereto. In addition, the product contains a higherpercentage of sulfur than is attainable when the reaction is conductedin the absence of a promoter. The products of the present invention canbe used, as prepared, for additives in lubri cating or cutting oils ormay be stripped of any unreacted or low boiling constituents before theyare so compounded. Clay filtration is one means of improving the colorcharacteristics of the product for certain purposes.

The typical commercial terpene, Dipentene 122, used to demonstrate thepresent invention, is a product made by the Hercules Powder Company,commonly referred to by the trade name, Dipentene 122. It is a mixtureof monoand dicyclic terpenes including dipentene, alpha terpinene,terpinolene, alpha pinene, beta pinene and 2,4 (8) paramenthadiene, withpara-cymene and para-menthane also present. Any one, or mixtures, ofthese terpenes may be used as starting materials for the preparation ofan additive, in accordance with this invention. The process is equallyapplicable to all of the monocyclic and dicyclic terpenes, which willreact with a sulfurizing agent, at a temperature of about the meltingpoint of sulfur to a temperature not exceeding the boiling point, ordecomposition point, of the terpene. Pine oil, turpentine, terpineol,carene, sabinene, and the diterpenes may also be used to the purposes ofthis invention. The specific example given was conducted underatmospheric pressures. However, it is possible to conduct the reactionusing sub-atmospheric or super-atmospheric pressures.

The amount of lead oxide promoter, used in accordance with thisinvention, may be from 1% to 15% by weight based on the total weight ofisoprenoid hydrocarbon to be treated. The addition of larger amounts hasno beneficial effect. For most reactions, from 1% to 5% of lead oxidepromoter will give the desired results. The promoter may be added at thebeginning of the reaction or it may be added in incremental portionsduring the reaction. The amount of each portion of promoter added,during the incremental addition, will be equivalent to about 20% of thetotal mass of lead oxide promoter used. By conducting the sulfurizationreactions in this manner, it is possible to take advantage of theexothermicity produced and thus maintain a high reaction rate during themajor part of the process.

The invention has been demonstrated by specific examples, whichillustrate the effectiveness and efficiency in which the sulfurizationreaction may be conducted with the new promoter. However, theillustration given should not be construed as limiting the invention.The only limitations appear in the following claims.

I claim:

1. The method, for preparing sulfurized isoprenoid hydrocarbons,comprising reacting said isoprenoid hydrocarbons with a sulfurizingagent present in an amount at least stoichiometrically equivalent tothat necessary to react with said isoprenoid hydrocarbons, at atemperature at least above the melting point of sulfur but below thedecomposition point of said isoprenoid hydrocarbons, and promoting saidreaction by the presence of a small amount of a promoter selected fromthe group consisting of lead oxides, hydrated lead oxides, metal saltsof lead acids and their mixtures.

2. The method, in accordance with claim 1, in which the promoter is leadtetraoxide.

3. The method, in accordance with claim 1, in which the promoter is leadsesquioxide.

4. The method, in accordance with claim 1, in which the promoter is leadperoxide.

5. The method, in accordance with claim 1, in which the promoter iscalcium orthoplumbate.

6. The method, in accordance with claim 1, in which the promoter ispotassium metaplumbate.

7. The method, in accordance with claim 1, in which the promoter is alead oxide present in from 1% to 15% by weight, based on the amount ofisoprenoid hydrocarbon.

8. The method, in accordance with claim 1, in which the sulfurizingagent is sulfur.

9. The method, in accordance with claim 1, in which the isoprenoidcompound is selected from the group consisting of monocyclic anddicyclic terpenes.

10. The method, in accordance with claim 1, in which the temperature ofthe reaction is between about 240 to 400 F.

11. The method of sulfurizing monoand dicyclic terpenes by reaction withsulfur, comprising heating said terpenes with an amount of sulfur atleast stoichiometrically sufiicient to react with said terpenes to atemperature of about 300 to 360 F. in the presence of about 1% to 15% byWeight of a promoter selected from the group consisting of lead oxides,hydrated lead oxides, metal salts of lead acids and their mixtures,until an exothermic reaction begins, interrupting said heating untilsaid exothermic reaction begins to subside, then heating the reactantsto a temperature of about 300 to 400 F. until a product is obtained fromwhich free sulfur does not precipitate on cooling to room temperature.

12. The method, in accordance with claim 11, in which the monoanddicyclic terpenes are selected from the group consisting of dipentene,alpha pinene, beta pinene, alpha terpinene, terpinolene, and theirmixtures.

13. The method, in accordance with claim 11, in which the promoter islead tetraoxide.

8 14. The method, in accordance with claim '11, in which the promoter islead sesquioxide.

15. The method, in accordance with claim 11, in which the promoter islead peroxide.

16. The method, in accordance with claim 11, in which the promoter iscalcium orthoplumbate. 1'7. The method, in accordance with claim 11, inwhich the promoter is potassium metaplumbate.

ELMER, W. BRENNAN.

References Cited in the file of this patent UNITED STATES PATENTS Number

1. THE METHOD, FOR PREPARING SULFURIZED ISOPRENOID HYDROCARBONS,COMPRISING REACTING SAID ISOPRENOID HYDROCARBONS WITH A SULFURIZINGAGENT PRESENT IN AN AMOUNT AT LEAST STOICHIOMETRICALLY EQUIVALENT TOTHAT NECESSARY TO REACT WITH SAID ISOPRENOID HYDROCARBONS, AT ATEMPERATURE AT LEAST ABOVE THE MELTING POINT OF SUFUR BUT BELOW THEDECOMPOSITION POINT OF SAID ISOPRENOID HYDROCARBONS, AND PROMOTING SAIDREACTION BY THE PRESENCE OF SMALL AMOUNT OF A PROMOTER SELECTED FROM THEGROUP CONSISTING OF LEAD OXIDES, HYDRATED LEAD OXIDES, METALS SALTS OFLEAD ACIDS AND THEIR MIXTURES.